In prior art air conditioning systems of this kind, batteries of ventilators are used, each of which comprises a tubular element fitted in a circular opening in the roof of the vehicle.
This tubular element is fitted with a plurality of radial arms which support a coaxial hub housing an electric motor whose output shaft drives an impeller or fan comprising a plurality of blades.
As is also known in prior art, these supporting arms are suitably shaped to regulate the flow of air generated by the impeller, thus improving the efficiency of the conditioning system and forming a fan duct together with the tubular element.
To protect the motor and prevent foreign objects from finding their way into the tubular element, with the risk of jamming the impeller, the circular opening in the vehicle roof is closed by a protective grille.
Looking in more detail at prior art, in a first solution, the tubular element and the motor are mounted in such a way that the impeller faces the outside of the vehicle, while the motor base extends into the vehicle. In this case, the fan is suitably protected by the grille which prevents access to the impeller blades.
In a second solution, the fan duct and the motor base extend outwards from the vehicle, while the impeller is inside the vehicle.
In this solution, too, the fan duct is protected by a grille which prevents foreign objects from finding their way into the tubular element.
These prior art solutions have inherent shortcomings, however.
Besides the obvious costs of making and assembling the protective grilles, these grilles counteract the action of the air flow regulating means, thus drastically reducing system efficiency.
Moreover, the grille also increases the noise produced by the ventilation system.